Abstract
	At the contemporary stage of the development of the engineering thought, and the product technology itself, material engineering has entered the period of new possibilities of designing and manufacturing of elements, introducing new methods of melting, casting, forming, and heat treatment of the casting materials, finding wider and wider applications in many industry branches. Engineers whose employment calls for significant expenditure of labour and costs strive to reduce material consumption. Therefore the development of engineering aims at designs optimizing, reducing dimensions, weight, and extending. Increasing the share of light structural materials in structures of airplanes or vehicles leads to reduction of environmental load. Magnesium alloys also play an important role among these materials. Aluminium and zinc are used the most frequently for alloying of magnesium. Small concentrations of manganese in the Mg-Al-Zn alloys improve resistance of these alloys to corrosion. Alloys AZ91 have been investigated very well and they found many applications in automotive industry. Mg-Al-Si alloys improve resistance to creep at temperatures up to 150 ?C, they have good plasticity, ultimate strength and yield strength. They are used in crank cases of air-cooled automobile engines, for production of clutch pistons and blade stators. In this paper there is presented the structure of the modeling cast magnesium alloys AZ91, AS31, alloy Mg-Zr, and pure magnesium. The presented work deals results of metallographic analysis; microanalysis and hardness measurements used alloys.